Petrol will run out, not fuly but it is all about how much it costs, it is slowly getting more expensive to get out of the ground, but while other technology is advancing more supplies are being found and drilling technology is getting beter so there is no certain answer but at some point it wont be worth the effort. I think we should use electric cars. use nuclear power to charge em up, we just need better batteries and faster electric cars. Eventually Fusion will replace Fissio and then we are sorted.
Biomass and lpg are nice but electric is the future.